1. Field of the Invention
The present invention relates to a wet stripping composition and process useful for silicate stripping, e.g., wet stripping removal of sacrificial anti-reflective silicate material from a substrate or article having such material deposited thereon, particularly where the sacrificial anti-reflective silicate material is present with permanent silicate materials desired to be unaffected by the wet stripping composition.
2. Description of the Related Art
During the fabrication of integrated circuits, silicate materials may be used as sacrificial layers, with the sacrificial layer being removed before completion of the device. U.S. Pat. No. 6,365,529 (assigned to Intel), “Method for Patterning Dual Damascene Interconnects Using a Light Absorbing Material,” describes a method for making dual-damascene structures using a dyed spin-on glass (SOG) material as a sacrificial anti-reflective coating that minimizes reflectivity variations during photolithographic patterning. Ultimately selective removal of the sacrificial material is necessary, which typically is effected by wet etching, using a wet etchant that demonstrates higher selectivity towards the sacrificial layer in relation to other materials that may be present in the structure, including inter-level dielectrics (ILD), metals, and barrier layers.
It is well-established that hydrogen fluoride (HF) solutions may be used to etch silicon oxide materials. However, HF solutions etch silicon oxides rapidly and non-selectively, and thereby may cause damage or loss of other silicate-containing materials in the device, especially silicate materials that are commonly used as ILDs. Such ILD materials include, by way of example, silicon dioxide, fluorinated silicate glass (FSG), and organosilicate glass (OSG), including both porous and non-porous materials.
In order to more carefully control the etch rate and selectivity of a fluoride solution towards silicon oxides, the HF acid solution may be buffered with amines or other bases such as ammonia or alkylamines, since buffering reduces the concentration of the active HF.
Additionally, the etch rate and/or selectivity of the fluoride solutions towards silicate glasses may be controlled by adding specific chelators to the solutions. The chelator interacts with the fluoride silicate reaction, and thus is capable of accelerating or retarding the etch rate. Chelators interact with different substrates by specific interactions that are both chelator-specific and substrate-specific. This specificity allows modification of the etch rate selectivity of a solution towards different substrates.
It would therefore be a substantial advance in the art to provide a wet cleaner that possesses high etch rate selectivity, i.e., high etch rate on a sacrificial silicate material and low etch rate on permanent silicate ILD materials, in applications where sacrificial and permanent silicates are both present in the original material.
Additionally, it would be desirable to provide a wet cleaner of such type that utilizes a safe, non-combustible solvent system, such as a semi-aqueous solvent system characterized by low toxicity and low combustibility.
These and other objects are achieved by the composition and method of the present invention, as hereinafter more fully described.
With reference to the present invention, as hereinafter more fully described, the state of the art forming a background to the present invention includes the following U.S. patents, the disclosures of which hereby are incorporated herein, in their respective entireties.
U.S. Pat. Nos. 5,698,503 and 5,571,447 (Ashland) describe a cleaning composition containing a glycol solvent, ammonium fluoride, dimethylsulfoxide, and water in a buffered acidic system having a pH of 4 to 7.
U.S. Pat. Nos. 5,630,904, 5,962,385 and 6,265,309 (Mitsubishi Gas) describe residue cleaning formulations for semiconductor substrates, in which the cleaning formulations contain fluoride, solvents and a buffer system.
U.S. Pat. Nos. 5,905,063 and 5,792,274 (Tokyo Ohka Kogyo) describe residue cleaning formulations for semiconductor substrates, in which the cleaning formulations contain a hydrofluoric acid salt with a metal-free base, solvents and a buffer system, having a pH of 5 to 8.
U.S. Pat. Nos. 6,235,693 and 6,248,704 (EKC Technology) describe cleaning formulations containing fluoride, water, and solvent(s), for cleaning residue from semiconductor substrates, in which the cleaning formulations have a pH of 6 to 10.
U.S. Pat. Nos. 6,365,765 and 6,268,457 (Honeywell) describe a method of making dyed spin-on glass (SOG) polymers by reacting alkoxysilanes with organic dyes, where the spin-on glass is used as a sacrificial anti-reflective coating (SARC).
U.S. Pat. No. 6,365,529 (Intel) describes a method for making dual damascene structures using a dyed spin-on glass (SOG) material as a SARC material.
U.S. Pat. No. 6,306,807 (ATMI) discloses formulations for cleaning post-plasma etch residues from semiconductor substrates, containing boric acid, amine(s), water, and optionally a glycol solvent or chelator.
U.S. Pat. No. 6,224,785 (ATMI) discloses formulations containing ammonium fluoride, amine(s), water, and a chelating agent, as useful for cleaning post plasma ash residues from semiconductor substrates.
U.S. Pat. No. 6,383,410 (ATMI) discloses formulations for selective etching of silicon oxides utilizing compositions containing fluoride salts, chelating agent, and glycol solvent.
U.S. Pat. No. 4,343,677 (Kinsbron et al.) discloses a formulation for etching silicon dioxide, utilizing ammonium fluoride/hydrofluoric acid in a molar ratio of about 10:1 in water/ethylene glycol.
None of the above patents, however, discloses or suggests a wet cleaner or method of wet stripping for the selective removal of sacrificial anti-reflective coatings (SARC) comprising a dyed silicate glass material. The present invention therefore achieves a substantial advance in the art, as will be more fully appreciated from the ensuing description.